This invention relates generally to electronic circuitry, and more specifically to a backplane printed circuit for routing digital and analog telephone signals among circuit cards connected to the backplane.
A number of conventional methods and systems are known for connecting telephone network lines to digital telephone exchange equipment. In one established technique, each network line is connected to a separate communication equipment printed circuit input card, and bus signal lines are connected from each such input card to processing circuitry. This method is advantageous in that each input card acts as a buffer to isolate one network line from another and from bus signal lines. However, each network line connection must be made directly to each card, and the network line cable must be detached from the input card in order to remove the input card for repair or replacement. In a typical exchange with a large number of network lines, such cable manipulation is awkward and confusing.
In a second conventional technique, all network line connections are grouped together within a single cable and are connected to a backplane via an input connection card or a connector directly on the backplane. This scheme permits easy removal and replacement of input cards, but typically results in undesired cross coupling of signals among network lines or between network lines and other signals in the telephone exchange equipment.
It would be desirable to provide a simple means of connection between network lines and digital exchange equipment in a manner that allows fast and easy replacement of input cards while providing good isolation of network lines.